Expression systems

Abstract

Expression systems which comprise a mammalian host, such as erythroid cells, transformed with a vector which comprises a promoter, a DNA sequence which codes for a desired polypeptide and a dominant control region. The vectors and methods for preparing polypeptides using the expression systems are also described. In a preferred embodiment, the vector contains cDNA for the desired polypeptide and a sequence which is capable of stabilising mRNA produced from the cDNA. The expression systems are particularly efficient and are capable of secreting the desired polypeptide.

We claim: 
     
       1. An expression system which comprises murine erythroleukemia cells transformed with a vector which comprises (i) the human beta-globin promoter, (ii) a genomic DNA sequence which codes for a polypeptide heterologous to said murine erythroleukemia cells and (iii) a dominant control region, and wherein after induction of differentiation of said murine erythroleukemia cells, said polypeptide is secreted by said murine erythroleukemia cells. 
     
     
       2. The expression system of claim 1 wherein the dominant control region comprises a micro locus which comprises a 6.5 kb fragment obtained by ligating the fragments: 2.1 kb XbaI - XbaI;   1.9 kb HindIII - HindIII;   1.5 kb KpnI - BgIII; and   1.1 kb partial SacI; from the β-globin gene.   
     
     
       3. A method of preparing a polypeptide, said method comprising cultivating the expression system according to claim 1. 
     
     
       4. An expression system which comprises murine erythroleukemia cells transformed with a vector which comprises (i) the human beta-globin promoter, (ii) the second exon/intron, 3rd exon and polyadenylation sequence, all of the human beta-globin gene, (iii) a cDNA sequence which codes for a polypeptide and (iv) a dominant control region, and wherein after induction of differentiation of said murine erythroleukemia cells, said polypeptide is secreted by said murine erythroleukemia cells. 
     
     
       5. The expression system of claim 4 wherein the dominant control region comprises a micro locus which comprises a 6.5 kb fragment obtained by ligating the fragments: 2.1 kb XbaI - XbaI;   1.9 kb HindIII - HindIII;   1.5 kb KpnI - BgIII ; and   1.1 kb partial SacI; from the β-globin gene.   
     
     
       6. A method of preparing a polypeptide, said method comprising cultivating the expression system according to claim 4.